Fans are employed in many homes to serve the function of moving stagnant air. The concept of securing a filter element to a blade of the fan in order to filter air thereby trapping air borne particles as the fan blade moves is taught in a number of references.
U.S. Pat. No. 4,753,573 which issued to McKnight in 1988 discloses a longitudinally extending channel member that is fixed by adhesive to a fan blade such that a filter element is supported in an upstanding position extending outwardly from the fan blade.
U.S. Pat. No. 4,840,650 which issued to Matherne in 1989 discloses a filter housing having clips which attach the filter housing to a leading edge of a fan blade.
U.S. Pat. No. 4,889,543 which issued to Burt in 1989 discloses a method and apparatus in which filter elements extend between adjacent circumferentially spaced apart fan blades.
It is readily apparent to an observer when a fan is equipped with one of the described devices. Some types of fans, for example ceiling fans serve a collateral decorative purpose. Great care is taken to make ceiling fans, aesthetically appealing to the consumer. Anything which potentially detracts from the aesthetic appearance of the fan is viewed as being undesirable.